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Geologic Unit: Exeter

Exeter Diorite (NH*)
Exeter Diorite of /Hillsboro plutonic series [informal] (NH)
["Hillsboro plutonic series" considered informal. The practice of employing "Series" for lithostratigraphic or lithodemic nomenclature is now regarded as improper. Term "Series" is applied formally only to chronostratigraphic units (ACSN, 1961, 1970; NACSN, 1983).]

Devonian, Early*
Geologic Province:
New England province*
Areal Extent:

Type Locality:
Exposures along Boston and Maine RR, between MA and ME, especially between towns of Exeter and Dover, Rockingham Co., southeastern NH (Hitchcock, 1870).

Unit Name History:
[Please note: only the post-1974 references include synopses here. The remaining references have yet to be added from the GNC index card files. Until then, feel free to contact us if you would like complete bibliographic citations.]
Named Exeter syenites (Hitchcock, 1870).
Revised to Exeter Diorite, described (Katz, 1917).
Assigned to New Hampshire plutonic series; Age modified (Billings, 1955).
Reassigned to Hillsboro plutonic series (Billings, 1956).
Age refined (Bothner, 1974).
Age modified (Goldsmith and others, 1982).
Not used in MA, equivalent rocks mentioned (Zen and others, 1983).
NH State Geol. Map usage; Age modified; Isotopic dating (Lyons and others, 1997).

Note: If you need more information, please contact Nancy Stamm (
Asterisks (*) indicate usage by the U.S. Geological Survey. Other usages by state geological surveys.

"No current usage" implies that a name has been abandoned or that it has fallen into disuse. Former usage and, if known, replacement name given in parentheses ().

Slashes (/) indicate unit name usage violates the 1983 North American Stratigraphic Code. This violation may be explained within brackets ([ ]).

U.S. Department of the Interior, U.S. Geological Survey, Reston, VA, USA
Database project personnel
Last modified: 15-Jan-2013